Image Sensors and Methods of Manufacturing Image Sensors

ABSTRACT

An image sensor includes a first substrate including a driving element, a first insulation layer on the first substrate and on the driving element, a second substrate including a photoelectric conversion element, and a second insulation layer on the second substrate and on the photoelectric conversion element. A surface of the second insulation layer is on an upper surface of the first insulation layer. The image sensor includes a conductive connector penetrating the second insulation layer and a portion of the first insulation layer. Methods of forming image sensors are also disclosed.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority under 35 USC §119 to Korean PatentApplication No. 10-2009-0100581, filed on Oct. 22, 2009, in the KoreanIntellectual Property Office (KIPO), the disclosure of which isincorporated herein in its entirety by reference.

BACKGROUND

1. Technical Field

The inventive concept relates to image sensors and methods ofmanufacturing image sensors. More particularly, the inventive conceptrelates to image sensors having highly integrated pixel arrays andmethods of manufacturing image sensors having highly integrated pixelarrays.

2. Description of the Related Art

Complementary metal-oxide semiconductor (CMOS) image sensors arebecoming more highly integrated. That is, they are being made smallerand/or to include more pixels. Each pixel of a typical CMOS image sensorincludes a photodiode and associated transistors for converting chargesgenerated in the photodiode into an electrical signal. As CMOS imagesensors become more highly integrated, the horizontal area of thephotodiode may be reduced. Therefore, the number of charges generated inthe photodiode may be reduced and/or interference between neighboringpixels (“crosstalk”) may increase, which can cause errors in the imagedata generated by the CMOS sensor.

SUMMARY

Some embodiments provide highly integrated image sensors and/or methodsof manufacturing a highly integrated image sensors.

According to some embodiments, an image sensor includes a firstsubstrate, a first oxide layer, a second substrate, a second oxide layerand a connector. The first substrate includes a driving element. Thefirst oxide layer is formed on the first substrate, where the firstoxide layer covers the driving element. The second substrate includes aphotoelectric conversion element. The second oxide layer is formed onthe second substrate, where the second oxide layer covers thephotoelectric conversion element and a surface of the second oxide layeris adhered to an upper surface of the first oxide layer. The connectorpenetrates the second substrate, the second oxide layer and a portion ofthe first oxide layer.

The driving element may include a reset transistor, a driving transistorand a selection transistor.

The photoelectric conversion element may include a photodiode.

The photoelectric conversion element may include a photodiode, atransfer transistor and a floating diffusion region.

The floating diffusion region may be provided under a surface of thesecond substrate between gate electrodes of the transfer transistors andbe commonly used by more than two unit pixels.

A wiring may be provided on the second substrate to electrically connectat least two floating diffusion regions.

The connector may be electrically connected to the wiring.

The first substrate may include a logic region and a logic circuit maybe provided on the logic region.

The connector may be provided for every four unit pixels.

In a method of manufacturing an image sensor according to someembodiments, a driving element is formed on a first substrate, a firstoxide layer is formed on the first substrate, where the first oxidelayer covers the driving element, a photoelectric conversion element isformed on a second substrate, a second oxide layer is formed on thesecond substrate, where the second oxide layer covers the photoelectricconversion element, the first substrate and the second substrate areadhered, and a connector penetrating the second substrate, the secondoxide layer and a portion of the first oxide layer is formed.

The photoelectric conversion element may include a photodiode, atransfer transistor and a floating diffusion region.

The floating diffusion region may be formed under a surface of thesecond substrate between gate electrodes of the transfer transistors.

A wiring may be formed in the second oxide layer, where the wiringelectrically connects at least two floating diffusion regions, a holepenetrating the wiring and a portion of the second oxide layer may beformed, and a sacrificial connector may be formed by depositing asacrificial layer in the hole.

The connector may be formed by etching a portion of the second substrateto expose the sacrificial connector, removing the sacrificial layer inthe sacrificial connector, forming a contact hole by etching the secondoxide layer and a portion of the first oxide layer disposed under thesacrificial layer, and depositing a conductive material in the contacthole.

The sacrificial layer may include a polymer material having carbon.

The photoelectric conversion element may include a photodiode.

A surface of the second substrate may be polished after adhering thefirst substrate and the second substrate, where the surface correspondsto an adhesion surface of the second substrate.

A color filter and a lens may be formed on the polished surface of thesecond substrate.

A logic circuit may be formed on the first substrate.

The sacrificial layer may be removed by an asking process.

An image sensor according to some further embodiments includes a firstsubstrate including a driving element, a first insulation layer on thefirst substrate and on the driving element, a second substrate includinga photoelectric conversion element, and a second insulation layer on thesecond substrate and on the photoelectric conversion element. A surfaceof the second insulation layer is on an upper surface of the firstinsulation layer. The image sensor further includes a conductiveconnector penetrating the second insulation layer and a portion of thefirst insulation layer.

The image sensor further includes a first wiring pattern between thefirst substrate and the first insulation layer, a second wiring patternbetween the second substrate and the second insulation layer, and afloating diffusion region in the second substrate. The second wiringpattern may be conductively connected to the floating diffusion region,and the first wiring pattern may be conductively connected to the secondwiring pattern by the conductive connector.

The driving element includes a reset transistor, a driving transistorand a selection transistor, and the photoelectric conversion elementincludes a photodiode, a transfer transistor and a floating diffusionregion. The floating diffusion region may be conductively connected to agate of the driving transistor by the conductive connector.

The floating diffusion region may be coupled to a source/drain region ofthe transfer transistor. In some embodiments, the floating diffusionregion provides the source/drain region of the transfer transistor.

The floating diffusion region may be conductively connected to asource/drain region of the reset transistor by the conductive connector.

The image sensor may further include a first wiring pattern between thefirst substrate and the first insulation layer, and a second wiringpattern between the second substrate and the second insulation layer.The second wiring pattern may be conductively connected to the floatingdiffusion region, and the first wiring pattern may be conductivelyconnected to the second wiring pattern by the conductive connector.

The image sensor may further include a second photodiode and a secondtransfer transistor in the second substrate. The floating diffusionregion may be coupled to source/drain regions of the first transfertransistor and the second transfer transistor.

The floating diffusion region may provide source/drain regions of thefirst transfer transistor and the second transfer transistor. In someembodiments, the conductive connector may be coupled to source/drainregions of four transfer transistors.

Methods of manufacturing an image sensor according to some furtherembodiments include forming a driving element on a first substrate,forming a first insulation layer on the first substrate and on thedriving element, forming a photoelectric conversion element on a secondsubstrate, forming a second insulation layer on the second substrate andon the photoelectric conversion element, adhering the first substrateand the second substrate, and forming a conductive connector thatpenetrates the second insulation layer and a portion of the firstinsulation layer.

The methods may further include forming a first wiring pattern betweenthe first substrate and the first insulation layer, a second wiringpattern between the second substrate and the second insulation layer,and a floating diffusion region in the second substrate. The secondwiring pattern may be conductively connected to the floating diffusionregion, and the first wiring pattern may be conductively connected tothe second wiring pattern by the conductive connector.

The driving element may include a reset transistor, a driving transistorand a selection transistor, and the photoelectric conversion element mayinclude a photodiode, a transfer transistor and a floating diffusionregion. The floating diffusion region may be conductively connected to agate of the driving transistor by the conductive connector. Furthermore,the floating diffusion region may be coupled to a source/drain region ofthe transfer transistor. In some embodiments, the floating diffusionregion may be conductively connected to a source/drain region of thereset transistor by the conductive connector.

The methods may further include forming at least two floating diffusionregions in the second substrate, and forming a wiring in the secondinsulation layer. The wiring electrically connects the at least twofloating diffusion regions and the conductive connector.

The methods may further include forming a wiring in the secondinsulation layer, forming a via hole that penetrates the wiring and aportion of the second insulation layer, forming a sacrificial connectorin the via hole, etching a portion of the second substrate to expose thesacrificial connector, removing the sacrificial connector, forming acontact hole by etching the second insulation layer and a portion of thefirst insulation layer disposed under the via hole, and depositing aconductive material in the contact hole. The sacrificial connectorincludes a polymer material including carbon.

The methods may further include polishing a surface of the secondsubstrate opposite the first substrate after adhering the firstsubstrate and the second substrate, and forming a color filter and alens on the polished surface of the second substrate.

The methods may further include forming a second photodiode and a secondtransfer transistor in the second substrate. The floating diffusionregion may be coupled to source/drain regions of the first transfertransistor and the second transfer transistor.

BRIEF DESCRIPTION OF THE DRAWINGS

Illustrative, non-limiting some embodiments will be more clearlyunderstood from the following detailed description taken in conjunctionwith the accompanying drawings.

FIG. 1 is a block diagram illustrating an image sensor in accordancewith some embodiments.

FIG. 2 is a circuit diagram illustrating an active pixel sensor (APS) ofan image sensor in accordance with some embodiments.

FIG. 3 is a cross-sectional view illustrating an image sensor inaccordance with some embodiments.

FIG. 4 is a top view of a second substrate included in an image sensorof FIG. 3.

FIGS. 5 to 20 are cross-sectional views illustrating methods ofmanufacturing an image sensor in accordance with some embodiments.

FIG. 21 is a cross-sectional view illustrating an image sensor inaccordance with some embodiments.

FIGS. 22 to 27 are cross-sectional views illustrating methods ofmanufacturing an image sensor in accordance with some embodiments.

FIG. 28 is a circuit diagram illustrating an inverter including a CMOStransistor.

FIG. 29 is a cross-sectional view of an inverter including a CMOStransistor in accordance with some embodiments.

FIGS. 30 and 31 are cross-sectional views for describing methods ofmanufacturing a CMOS transistor of FIG. 29.

FIG. 32 is a block diagram illustrating a system including an imagesensor in accordance with some embodiments.

FIGS. 33 and 34 are a cross-sectional views illustrating image sensorsin accordance with further embodiments.

DESCRIPTION OF THE EMBODIMENTS

Various some embodiments will be described more fully hereinafter withreference to the accompanying drawings, in which some embodiments areshown. The present inventive concept may, however, be embodied in manydifferent forms and should not be construed as limited to the someembodiments set forth herein. Rather, these embodiments are provided sothat this disclosure will be thorough and complete, and will fullyconvey the scope of the present inventive concept to those skilled inthe art. In the drawings, the sizes and relative sizes of layers andregions may be exaggerated for clarity. Like numerals refer to likeelements throughout.

It will be understood that, although the terms first, second, third etc.may be used herein to describe various elements, these elements shouldnot be limited by these terms. These terms are used to distinguish oneelement from another. Thus, a first element discussed below could betermed a second element without departing from the teachings of thepresent inventive concept. As used herein, the term “and/or” includesany and all combinations of one or more of the associated listed items.

It will be understood that when an element is referred to as being“connected” or “coupled” to another element, it can be directlyconnected or coupled to the other element or intervening elements may bepresent. In contrast, when an element is referred to as being “directlyconnected” or “directly coupled” to another element, there are nointervening elements present. Other words used to describe therelationship between elements should be interpreted in a like fashion(e.g., “between” versus “directly between,” “adjacent” versus “directlyadjacent,” etc.).

The terminology used herein is for the purpose of describing particularsome embodiments only and is not intended to be limiting of the presentinventive concept. As used herein, the singular forms “a,” “an” and“the” are intended to include the plural forms as well, unless thecontext clearly indicates otherwise. It will be further understood thatthe terms “comprises” and/or “comprising,” when used in thisspecification, specify the presence of stated features, integers, steps,operations, elements, and/or components, but do not preclude thepresence or addition of one or more other features, integers, steps,operations, elements, components, and/or groups thereof.

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which this inventive concept belongs. Itwill be further understood that terms, such as those defined in commonlyused dictionaries, should be interpreted as having a meaning that isconsistent with their meaning in the context of this specification andthe relevant art and will not be interpreted in an idealized or overlyformal sense unless expressly so defined herein.

FIG. 1 is a block diagram illustrating an image sensor in accordancewith some embodiments. FIG. 2 is a circuit diagram illustrating anactive pixel sensor (APS) of an image sensor in accordance with someembodiments.

Referring to FIG. 1, the image sensor includes an active pixel sensor(APS) array 90 and logic circuits. The APS array 90 may include aplurality of unit pixels. The logic circuits may include a timinggenerator 20, a row decoder 30, a row driver 40, a correlated doublesampler (CDS) 50, an analog to digital converter (ADC) 60, a latch unit70 and a column decoder 80.

In some embodiments, unit elements included in the APS array 90 may bedisposed both on a first substrate and a second substrate. The logiccircuits may be provided on the first substrate.

The unit pixel in the APS array 90 may include a photodiode and aplurality of transistors. When the unit pixel has a three-transistorconstruction, only the photodiode among the photodiode and the pluralityof transistors may be disposed on the second substrate. When the unitpixel has a four-transistor construction, the photodiode and a transfertransistor may be disposed on the second substrate.

Hereinafter, the active pixel sensor in the image sensor will bedescribed with reference to FIG. 2.

The active pixel sensor may convert an optical image into an electricalsignal. The active pixel sensor may have a four shared pixelconstruction in which a first photodiode PD1, a second photodiode PD2, athird photodiode PD3 and a fourth photodiode PD4 are electricallyconnected to a common floating diffusion region FD to share readelements.

Referring to FIG. 2, the active pixel sensor includes the firstphotodiode PD1, the second photodiode PD2, the third photodiode PD3, thefourth photodiode PD4, a first transfer transistor TX1 electricallyconnected to the first photodiode PD1, a second transfer transistor TX2electrically connected to the second photodiode PD2, a third transfertransistor TX3 electrically connected to the third photodiode PD3 and afourth transfer transistor TX4 electrically connected to the fourthphotodiode PD4. The first transfer transistor TX1, the second transfertransistor TX2, the third transfer transistor TX3 and the fourthtransfer transistor TX4 are electrically connected to the commonfloating diffusion region FD. Charges stored in the first to the fourthphotodiodes PD1, PD2, PD3 and PD4 may be transferred into the commonfloating diffusion region FD through the first to the fourth transfertransistors TX1, TX2, TX3 and TX4, respectively.

As illustrated in FIG. 2, the first to the fourth photodiodes PD1, PD2,PD3 and PD4, the first to the fourth transfer transistors TX1, TX2, TX3and TX4, and the common floating diffusion region FD are disposed on thesecond substrate.

The common floating diffusion region FD may be electrically connected toa driving transistor FX. The driving transistor FX may be a sourcefollower amplifier. The driving transistor FX may amplify a change in anelectrical potential of the common floating diffusion region FD.

A reset transistor RX may be electrically connected to the commonfloating diffusion region FD and reset the electrical potential of thecommon floating diffusion region FD periodically. The reset transistorRX may reset the electrical potential of the common floating diffusionregion FD using a bias voltage. For example, the reset transistor RX mayreset the electrical potential of the common floating diffusion regionFD by connecting a power supply voltage VCC to the common floatingdiffusion region FD.

A selection transistor SX may select a row including four shared pixelsin response to a bias voltage provided through a selection line andprovide an output of the driving transistor FX to an output line VOUT.

As illustrated in FIG. 2, the driving transistor FX, the resettransistor RX and the selection transistor SX are disposed on the firstsubstrate. The read elements including the driving transistor FX, thereset transistor RX and the selection transistor SX may be shared by thefour photodiodes PD1, PD2, PD3 and PD4. The read elements including thedriving transistor FX, the reset transistor RX and the selectiontransistor SX may read each of a light signal incident on the four photodiodes PD1, PD2, PD3 and PD4.

As described above, the driving transistor FX, the reset transistor RXand the selection transistor SX are disposed on the first substrate, andthe first to the fourth photodiodes PD1, PD2, PD3 and PD4, the first tothe fourth transfer transistors TX1, TX2, TX3 and TX4 and the commonfloating diffusion region FD are disposed on the second substrate. Thelogic circuits are disposed on the first substrate. The image sensoraccording to some embodiments may have a three dimensional constructionsince the first substrate and the second substrate may be adhered toeach other.

FIG. 3 is a cross-sectional view illustrating an image sensor inaccordance with some embodiments, and FIG. 4 is a top view of a secondsubstrate included in an image sensor of FIG. 3.

Hereinafter, the image sensor will be described in detail with referenceto FIGS. 3 and 4. In FIG. 3, a reference numeral 150 represents elementsprovided on a first substrate 100 and a reference numeral 250 indicateselements positioned on a second substrate 200 a.

Referring to FIG. 3, the first substrate 100 may include a singlecrystalline material. For example, the first substrate 100 may includesingle crystalline silicon, single crystalline germanium, etc. The firstsubstrate 100 includes an active pixel region and a logic region. Aselection transistor 106, a driving transistor 104 and a resettransistor 102 are disposed in the active pixel region. A transistor 108included in the logic circuits is located in the logic region. Each ofthe transistors 102, 104, 106 and 108 on the first substrate 100 mayinclude a gate insulation layer, a gate electrode and impurity regions.A spacer may be provided on a sidewall of each gate electrode.

A first insulation layer 110, a second insulation layer 114, a thirdinsulation layer 118, a fourth insulation layer 122 and a fifthinsulation layer 126 covering the transistors 102, 104, 106 and 108 aresequentially disposed on the first substrate 100. A first wiring 112, asecond wiring 116, a third wiring 120 and a fourth wiring 124 are formedthrough the first to the fifth insulation layers 110, 114, 118, 122 and126, respectively. The first to the fourth wirings 112, 116, 120 and 124may be electrically connected to the transistors 102, 104, 106 and 108on the first substrate 100. Each of the first to the fourth wirings 112,116, 120 and 124 includes a contact plug and a conductive pattern. Theconductive pattern may have a line shape or a pad shape. The first tothe fifth insulation layers 110, 114, 118, 122 and 126 may includesilicon oxide. The first to the fourth wirings 112, 116, 120 and 124 mayinclude polysilicon, metal, metal nitride, metal silicide, etc. In someembodiments, the first to the fourth wirings 112, 116, 120 and 124 mayinclude a material such as tungsten being easily patterned by aphotolithography process.

The first insulation layer 110, the first wiring 112, the secondinsulation layer 114, the second wiring 116, the third insulation layer118, the third wiring 120, the fourth insulation layer 122 and thefourth wiring 124 are sequentially provided on the first substrate 100.The first wiring 112 may be directly connected to the impurity regionsand the gate electrodes of the transistors 102, 104, 106 and 108. Thesecond wiring 116 may be electrically connected to the impurity regionsof the reset transistor 102 and the gate electrode of the drivingtransistor 104. Additionally, the second wiring 116 may be electricallyconnected to the gate electrode of the selection transistor 106. Thethird wiring 120 may make electrical contact with the gate electrode ofthe reset transistor 102. The fourth wiring 124 may be electricallyconnected to the second wiring 116.

A conductive pattern 124 a (see FIG. 4) of the fourth wiring 124 mayhave a shape extending in a direction substantially parallel to thefirst substrate 100. The conductive pattern 124 a may have an areasubstantially the same as or substantially similar to a sum ofhorizontal areas of the four photodiodes PD1, PD2, PD3 and PD4. Forexample, the conductive pattern 124 a may have a rectangular shape eachside of which may be substantially larger than about 1.2 μm.

The first to the fourth wirings 112, 116, 120 and 124 are also providedin the logic region of the first substrate 100. The first to the fourthwirings 112, 116, 120 and 124 may be electrically connected to the logiccircuits in the logic region.

The fifth insulation layer 126 covering the fourth wiring 124 is locatedon the first substrate 100. The fifth insulation layer 126 may includeoxide such as silicon oxide. For example, the fifth insulation layer 126may include high density plasma-chemical vapor deposition (HDP-CVD)oxide. The fifth insulation layer 126 may have a thickness of about1,500 Å to about 3,500 Å measured from an upper surface of theconductive pattern 124 a of the fourth wiring 124.

Referring now to FIGS. 3 and 4, the second substrate 200 a may alsoinclude a single crystalline material. For example, the second substrate200 a may include single crystalline silicon or single crystallinegermanium. The second substrate 200 a may be obtained by an epitaxialprocess.

An isolation layer pattern 201 is disposed in the second substrate 200a. The isolation layer pattern 201 may have a predetermined thicknessfrom a first surface A of the second substrate 200 a. The isolationlayer pattern 201 may electrically isolate photodiodes 210 from eachother. In some embodiments, the isolation layer pattern 201 mayelectrically isolate the photodiodes 210 by a unit of two adjacentphotodiodes.

The photodiodes 210 are provided in the second substrate 200 a. Each ofthe photodiodes 210 may also have predetermined depth from the firstsurface A of the second substrate 200 a. The photodiode 210 may includea first impurity region and a second impurity region located on thefirst impurity region. For example, the first impurity region mayinclude N-type impurities whereas the second impurity region may includeP-type impurities.

A transfer transistor 214 is positioned on the first surface A of thesecond substrate 200 a. The transfer transistor 214 may be disposedadjacent to one end of the photodiode 210. In some embodiments, onetransfer transistor 214 may be electrically connected to one photodiode210. A gate electrode of the transfer transistor 214 may protrudedownwardly (that is, toward the first substrate 100) from the firstsurface A of the second substrate 200 a. Two adjacent transfertransistors 214 may share one common impurity region. For example, twoadjacent transfer transistors 214 may include one common source region.

A floating diffusion region 212 is provided beneath the first surface Aof the second substrate 200 a between two adjacent transfer transistors214. The floating diffusion region 212 may serve as the common impurityregion of the two transfer transistors 214 so that two adjacent transfertransistors 214 may share the floating diffusion region 212. Chargesstored in the photodiodes 210 may be transferred into the floatingdiffusion region 212 through the transfer transistors 214.

An eighth insulation layer 218, a seventh insulation layer 222 and asixth insulation layer 228, which cover the transfer transistor 214, thefloating diffusion region 212 and the photodiode 210, are successivelydisposed under the first surface A of the second substrate 200 a. Asixth wiring 220 and a fifth wiring 224 are disposed through the eighthto the sixth insulation layers 218, 222 and 228 to be electricallyconnected to the transfer transistor 214 and the floating diffusionregion 212. The eighth to the sixth insulation layers 218, 222 and 228may include oxide, for example, silicon oxide. The sixth and the fifthwirings 220 and 224 may include polysilicon, metal, metal nitride, metalsilicide, etc. In some embodiments, the sixth and the fifth wirings 220and 224 may include a material such as tungsten being easily patternedby a photolithography process.

The eighth insulation layer 218 covers the floating diffusion region212, the photodiode 210 and the transfer transistor 214. The sixthwiring 220, the seventh insulation layer 222 and the fifth wiring 224are successively provided under the first surface A of the secondsubstrate 200 a. The sixth wiring 220 may be directly connected to theimpurity region, the gate electrode and the floating diffusion region212 of the transfer transistor 214. The fifth wiring 224 mayelectrically connect one floating diffusion region 212 to an adjacentfloating diffusion region 212. When two adjacent floating diffusionregions 212 are connected to each other by the fifth wiring 224, thefour photodiodes PD1, PD2, PD3 and PD4 may share a common floatingdiffusion region.

The sixth insulation layer 228 covering the fifth wiring 224 is providedunder the first surface A of the second substrate 200 a. A lower surfaceof the sixth insulation layer 228 may make contact with an upper surfaceof the fifth insulation layer 126. The sixth insulation layer 228 mayinclude a material substantially the same as or substantially similar tothat of the fifth insulation layer 126. For example, the sixthinsulation layer 228 may include HPD-CVD oxide. The sixth insulationlayer 228 may have a thickness of about 1,500 Å to about 3,500 Å basedon a lower surface of a conductive pattern 224 a of the fifth wiring224. A total thickness of the fifth insulation layer 126 and the sixthinsulation layer 228 may be in a range of about 5,500 Å to about 7,000 Åbetween the fourth wiring 124 and the fifth wiring 224.

A P-well (not illustrated) is located in the second substrate 200 a froma second surface B of the second substrate 200 a. An N-well 204 isprovided in the second substrate 200 a beneath the P-well. The N-well204 may correspond to the photodiode 210. The N-well 204 may be disposedto be spaced apart from the photodiode 210. The P-well and the N-well204 may prevent or discourage negative charges generated by an incidentlight from undesirably moving toward a photodiode included in anadjacent pixel.

A connecting member penetrates the second substrate 200 a, the eighth tothe sixth insulation layers 218, 222 and 228, and the sixth and thefifth wirings 220 and 224 from the second surface B of the secondsubstrate 200 a. The connecting member is electrically connected to thefourth wiring 124 on the first substrate 100. In some embodiments, theconnecting member may include a contact plug 236. The sixth and thefifth wirings 220 and 224 positioned on the second substrate 200 a andthe first to the fourth wirings 112, 116, 120 and 124 located on thefirst substrate 100 may be electrically connected to one another by thecontact plug 236. The contact plug 236 may include a conductivematerial, such as polysilicon, a metal and/or a metal compound. Thecontact plug 236 may have a relatively small width, for example, in arange of about 180 nm to about 220 nm. Additionally, the contact plug236 may extend into the structure by a depth of about 2 μm or more.

As illustrated in FIG. 3, the contact plug 236 electrically may connectthe floating diffusion region 212 on the second substrate 200 a to thetransistors 102, 104, 106 and 108 on the first substrate 100.

Two adjacent floating diffusion regions 212 on the second substrate 200a may be connected to each other by the fifth wiring 224 and the sixthwiring 220. The four photodiodes PD1, PD2, PD3 and PD4 and the fourtransfer transistors TX1, TX2, TX3 and TX4 may share the common floatingdiffusion regions 212. Thus, one contact plug 236 may be provided forthe four photodiodes PD1, PD2, PD3 and PD4. As a result, the number ofthe contact plug 236, which penetrates from the second substrate 200 ato the first substrate 100, may be reduced because a plurality ofphotodiodes and a plurality of transfer transistors may have the commonfloating diffusion regions 212.

An anti-reflective layer 238 is provided on the second surface B of thesecond substrate 200 a. The anti-reflective layer 238 may prevent ordiscourage an incident light from reflecting on the second surface B ofthe second substrate 200 a. The anti-reflective layer 238 may includesilicon nitride, silicon oxynitride, tantalum oxide, titanium oxide,hafnium oxide, etc. These may be used alone or in a combination thereof.The anti-reflective layer 238 may have a thickness in a range of severaltens of angstroms up to several hundreds of angstroms.

A color filter 240 is provided on the anti-reflective layer 238, and amicro lens 242 is disposed on the color filter 240. The color filter 240and the micro lens 242 may be positioned over the active pixel region ofthe first substrate 100.

Further embodiments are illustrated in FIG. 34, which is across-sectional view illustrating an image sensor in accordance withsome embodiments. The embodiments of FIG. 34 are similar to theembodiments illustrated in FIG. 3, except as described below. As shownin FIG. 34, a conductive contact plug 246 may not extend into or to thesurface of the second substrate 200 a. Rather, the conductive contactplug 246 may be formed to partially fill a via that extends through thesecond substrate 200 a to the fourth wiring 124. An insulation material241, such as silicon oxide, may be deposited in the via above theconductive contact plug 246, and may extend from the second surface B ofthe second substrate 200 a to or into the eighth insulation layer 218.The conductive contact plug 246 may electrically connect the fourthwiring 124, the fifth wiring 224, and the sixth wiring 220.

FIGS. 5 to 20 are cross-sectional views illustrating methods ofmanufacturing image sensors in accordance with some embodiments. In someembodiments, image sensors may be obtained by combining a firstsubstrate with a second substrate after forming a plurality elements andwirings on the first substrate and the second substrate.

Referring to FIG. 5, a second substrate 200 including a singlecrystalline silicon layer 200 a is provided. The single crystallinesilicon layer 200 a may be formed on the second substrate 200 by anepitaxial process. Hereinafter, an upper surface of the singlecrystalline silicon layer 200 a is referred to as a first surface of thesecond substrate 200 and a lower surface of the second substrate 200 isreferred to as a second surface of the second substrate 200. The secondsubstrate 200 may be doped with P-type impurities.

Isolation layer patterns (not illustrated) may be formed in the secondsubstrate 200 from the first surface of the second substrate 200 by anisolation process. For example, the isolation process may include ashallow trench isolation (STI) process, a local oxidation of silicon(LOCOS) process, etc.

An N-well 204 is formed in the second substrate 200 by implanting anddiffusing N-type impurities from the first surface of the secondsubstrate 200. In some embodiments, a P-well may be formed in the secondsubstrate 200 when N-type impurities are previously doped into thesecond substrate 200. That is, the conductive types of the well and thesecond substrate 200 may vary as conductive types of transistors,photodiodes, etc.

A photodiode 210, a transfer transistor 214 and a floating diffusionregion 212 are formed on the first surface of the second substrate 200.

In some embodiments, a parasitic capacitor among between a gate of adriving transistor FX, a drain of a reset transistor RX and a metalcontact of the transfer transistor 214 may be used as the floatingdiffusion region 212 without forming an additional floating diffusionregion.

According to some embodiments, an N-type photodiode region 206 is formedby doping N-type impurities under the first surface of the secondsubstrate 200. A gate of the transfer transistor 214 is formed on thefirst surface of the second substrate 200, and a spacer 216 is formed ona sidewall of the gate of the transfer transistor 214. A P-typephotodiode region 208 is formed on the N-type photodiode region 206 bydoping P-type impurities beneath the first surface of the secondsubstrate 200. The floating diffusion region 212 is formed in the firstsurface of the second substrate 200 by implanting impurities betweengate electrodes of the transfer transistors 214. Adjacent transfertransistors 214 may share one common floating diffusion region 212.

Referring to FIG. 6, an eighth insulation layer 218 covering thephotodiode 210, the floating diffusion region 212 and the transfertransistor 214 is formed on the second substrate 200 having the singlecrystalline silicon layer 200 a.

First contact plugs are formed through the eighth insulation layer 218.The first contact plugs may make contact with the gate of the transfertransistor 214 and the floating diffusion region 212. A first conductivepattern is formed on the eighth insulation layer 218 to be connected tothe first contact plug. The first conductive pattern may be formed bydepositing a conductive material and patterning the deposited conductivematerial by a photolithography process.

In some embodiments, the first contact plug and the first conductivepattern together serve as a sixth wiring 220. The first contact plug mayinclude a material substantially the same as or substantially similar tothat of the first conductive pattern. Alternatively, the first contactplug and the first conductive pattern may include different materials,respectively. For example, the first contact plug and the firstconductive pattern may include polysilicon, metal, metal nitride, metalsilicide, etc. In some embodiments, the first conductive pattern mayinclude tungsten considering an etching process for forming the firstconductive pattern.

Referring to FIG. 7, a seventh insulation layer 222 is formed on theeighth insulation layer 218. The seventh insulation layer 222 maysufficiently cover the sixth wiring 220.

A second contact plug is formed through the seventh insulation layer 222and to contact with the first conductive pattern. A second conductivepattern is formed on the seventh insulation layer 222 to be connected tothe second contact plug. The second contact plug and the secondconductive pattern may serve together as a fifth wiring 224. The fifthwiring 224 may be electrically connected to the sixth wiring 220. Forexample, the second contact plug may make contact with the firstconductive pattern.

An additional insulation layer (not illustrated) is formed to cover thesecond conductive pattern, and then the additional insulation layer isplanarized to expose an upper surface of the second conductive pattern.Thus, the second conductive pattern and the seventh insulation layer 222may have level surfaces. Alternatively, the additional insulation layermay not be planarized as occasion demands.

Referring to FIG. 8, first contact holes 217 are formed through theseventh and the eighth insulation layer 222 and 218 by an etchingprocess. The first contact holes 217 may penetrate at least one of thesecond conductive pattern and the first conductive pattern. The firstcontact holes 217 expose the first surface of the second substrate 200.In some embodiments, some of the first contact holes 217 may penetratethe second conductive pattern and the first conductive pattern throughthe seventh insulation layer 222 and the eighth insulation layer 218.Others of the first contact holes 217 may penetrate the first conductivepattern through the seventh insulation layer 222 and the eighthinsulation layer 218 without contacting the fifth wiring 224. The firstcontact holes 217 may expose portions of the second substrate 200 onwhich the photodiode 210 and the transfer transistor 214 are not formed.

Referring to FIG. 9, a sacrificial layer (not illustrated) is formed onthe fifth wiring 224 and the seventh insulation layer 222 to fill up thefirst contact holes 217. The sacrificial layer may be formed using amaterial being easily removed by an ashing process. For example, thesacrificial layer may be formed using a carbon-containing material suchas polymer including carbon.

Sacrificial plugs 230 are formed in the first contact holes 217 byplanarizing the sacrificial layer to expose upper surfaces of the fifthwiring 224 and the seventh insulation layer 222.

Referring to FIG. 10, a sixth insulation layer 228 is formed on theseventh insulation layer 222 and the sacrificial plugs 230. The sixthinsulation layer 228 may include oxide such as silicon oxide. Forexample, sixth insulation layer 228 may include HDP-CVD oxide. As willbe described later, an upper surface of the sixth insulation layer 228may make contact with the first substrate. Any conductive materials arenot exposed on the upper surface of the sixth insulation layer 228. Onlyoxide such as silicon oxide is exposed on the upper surface of the sixthinsulation layer 228.

The sixth insulation layer 228 is preferred to have a level uppersurface since the upper surface of the sixth insulation layer 228 maymake contact with the first substrate. As described above, the seventhinsulation layer 222 and the fifth wiring 224 may have level uppersurfaces. As a result, the sixth insulation layer 228 may have a levelupper surface without an additional planarization process.

When the sixth insulation layer 228 has a thickness of less than about1000 Å, the sixth insulation layer 228 may not perform an insulatingfunction. When the sixth insulation layer 228 has a thickness of morethan about 3500 Å, it is hard to etch the sixth insulation layer 228 infollowing etching processes. Therefore, the sixth insulation layer 228may have a thickness of about 1000 Å to about 3500 Å.

Referring to FIG. 11, a first substrate 100 including a singlecrystalline silicon is provided. A bulk silicon substrate may be used asthe first substrate 100. Isolation layer patterns (not illustrated) maybe formed in the first substrate 100 by an isolation process. The firstsubstrate 100 includes an active pixel region and a logic region.

A selection transistor 106, a driving transistor 104 and a resettransistor 102 are disposed in the active pixel region. A transistor 108included in the logic circuits is located in the logic region.

Gates 102 a, 104 a and 106 a of the reset transistor 102, the drivingtransistor 104 and the selection transistor 106, respectively, may beformed on a first surface of the first substrate 100 in the active pixelregion. A gate 108 a of the transistor 108 may be formed on the firstsurface of the first substrate 100 in the logic region. Impurity regions102 b, 104 b, 106 b and 108 b, which serve as source regions and drainregions, may be formed by implanting impurities beneath the firstsurface of the first substrate 100 around both sides of the gates 102 a,104 a, 106 a and 108 a.

Referring to FIG. 12, a first insulation layer 110 covering thetransistors 102, 104, 106 and 108 is formed on the first substrate 100.

Third contact plugs are formed through the first insulation layer 110.The third contact plugs may make contact with the gates and the impurityregions of the reset transistor 102, the driving transistor 104, theselection transistor 106 and the transistor 108.

A third conductive pattern is formed on the first insulation layer 110to be connected to the third contact plug. The third conductive patternmay be formed by depositing a conductive material and patterning thedeposited conductive material by a photolithography process.

In some embodiments, the third contact plug and the third conductivepattern together may serve as a first wiring 112. The third contact plugmay include a material substantially the same as or substantiallysimilar to that of the third conductive pattern. Alternatively, thethird contact plug and the third conductive pattern may includedifferent materials, respectively. For example, the third contact plugand the third conductive pattern may include polysilicon, metal, metalnitride, metal silicide, etc. In some embodiments, the third conductivepattern may include tungsten considering an etching process forming thethird conductive pattern.

Referring to FIG. 13, a second insulation layer 114 is formed on thefirst insulation layer 110. The second insulation layer 114 maysufficiently cover the first wiring 112. A fourth contact plug is formedthrough the second insulation layer 114 and to contact with the thirdconductive pattern. The fourth contact plug may be electricallyconnected to one of the impurity regions of the reset transistor 102,the gate of the driving transistor 104 and the gate of the selectiontransistor 106.

A fourth conductive pattern is formed on the second insulation layer 114to be connected to the fourth contact plug. The fourth contact plug andthe fourth conductive pattern together may serve as a second wiring 116.The fourth conductive pattern may electrically connect adjacent fourthcontact plugs to each other. For example, the fourth conductive patternmay connect the fourth contact plug contacting with the impurity regionof the reset transistor 102 to the fourth contact plug contacting withthe gate of the driving transistor 104. In this way, the impurity regionof the reset transistor 102 may be connected to the gate of the drivingtransistor 104. The fourth contact plug and the fourth conductivepattern are also provided in the logic region of the first substrate100.

The third insulation layer 118 is formed on the second insulation layer114. A fifth contact plug is formed through the third insulation layer118 and the second insulation layer 114 and to contact with the thirdconductive pattern. For example, the fifth contact plug may make contactwith the gate of the reset transistor 102.

A fifth conductive pattern is formed on the third insulation layer 118to be connected to the fifth contact plug. The fifth contact plug andthe fifth conductive pattern together may serve as a third wiring 120.The fifth contact plug and the fifth conductive pattern are alsoprovided in the logic region of the first substrate 100.

Referring to FIG. 14, a fourth insulation layer 122 is formed on thethird insulation layer 118. A sixth contact plug is formed through thefourth insulation layer 122 and the third insulation layer 118 tocontact with the fourth conductive pattern. As illustrated in FIG. 14,the sixth contact plug may make contact with the fourth conductivepattern connecting the impurity region of the reset transistor 102 tothe gate of the driving transistor 104.

A sixth conductive pattern 124 a is formed on the fourth insulationlayer 122 to be connected to the sixth contact plug. The sixth contactplug and the sixth conductive pattern 124 a together may serve as afourth wiring 124. The sixth contact plug and the sixth conductivepattern 124 a are also provided in the logic region of the firstsubstrate 100.

The sixth conductive pattern 124 a is a topmost conductive pattern amongthe third to the sixth conductive patterns on the first substrate 100.As will be described later, the sixth conductive pattern 124 a may beelectrically connected to the first and/or the second conductive patternof the second substrate 200. Therefore, the sixth conductive pattern 124a is preferred to have a large horizontal area, so that the sixthconductive pattern 124 a of the first substrate 100 and the first andthe second conductive patterns on the second substrate 200 may beelectrically connected to each other without a misalignment. The sixthconductive pattern 124 a of the first substrate 100 may have a shapeextending in a direction substantially parallel to the first substrate100.

The image sensor according to some embodiments may have a four sharedpixel construction in which four photodiodes share read elements.Therefore, the sixth conductive pattern 124 a may have as much areasubstantially the same as or substantially similar to a sum ofhorizontal areas of four photodiodes formed in the second substrate 200.

The sixth conductive pattern 124 a provided in the logic region also hasa large horizontal area to increase an alignment margin.

An additional insulation layer (not illustrated) is formed to cover thesixth conductive pattern 124 a, and then the additional insulation layeris planarized to expose an upper surface of the sixth conductive pattern124 a. A fifth insulation layer 126 is formed on the additionalinsulation layer and the sixth conductive pattern 124 a. The fifthinsulation layer 126 may include a material substantially the same as orsubstantially similar to that of the sixth insulation layer 228. Forexample, the fifth insulation layer 126 may include HDP-CVD oxide.

As will be described later, an upper surface of the fifth insulationlayer 126 may make contact with the second substrate 200. Any conductivematerials are not exposed on the upper surface of the fifth insulationlayer 126. Only oxide such as silicon oxide is exposed on the uppersurface of the fifth insulation layer 126.

The fifth insulation layer 126 may have a thickness of about 1,500 Å toabout 3,500 Å measured from an upper surface of the sixth conductivepattern 124 a. A total thickness of the fifth insulation layer 126 onthe first substrate 100 and the sixth insulation layer 228 on the secondsubstrate 200 may be less than about 7,000 Å. When the total thicknessof the fifth insulation layer 126 and the sixth insulation layer 228 ismore than about 7,000 Å, it is hard to etch the fifth insulation layer126 and the sixth insulation layer 228 in following etching processes.The total thickness of the fifth insulation layer 126 and the sixthinsulation layer 228 may be in a range of about 5,000 Å to about 6,000Å.

Referring to FIG. 15, the fifth insulation layer 126 on the firstsubstrate 100 and the sixth insulation layer 228 on the second substrate200 are adhered to each other by aligning, contacting and compressingthe fifth insulation layer 126 and the sixth insulation layer 228, andperforming a thermal treatment on two compressed insulation layers. Atleast a portion of the fourth wiring 124 on the first substrate 100 maycorrespond to the sacrificial plug 230 on the second substrate 200.

Since the sixth conductive pattern 124 a on the first substrate 100 hasa shape extending in a direction substantially parallel to the firstsubstrate 100, it is easy to align the first substrate 100 with thesecond substrate 200, such that the sixth conductive pattern 124 a maycorrespond to the sacrificial plug 230. For example, the sixthconductive pattern 124 a may have a rectangular shape each side of whichmay be substantially larger than about 1.2 μm. In this case, analignment margin between the sixth conductive pattern 124 a and thesacrificial plug 230 may be enlarged to about 1.2 μm along bothx-direction and y-direction.

Hereinafter, a process for adhering the fifth insulation layer 126 onthe first substrate 100 to the sixth insulation layer 228 on the secondsubstrate 200 will be described. At first, surfaces of the fifthinsulation layer 126 and the sixth insulation layer 228 may be cleanedfor removing particles from the surfaces of the fifth insulation layer126 and the sixth insulation layer 228. The surface of the fifthinsulation layer 126 may be aligned and contacted with the surface ofthe sixth insulation layer 228, and a thermal treatment is performed onthe surfaces of the fifth insulation layer 126 and the sixth insulationlayer 228 to increase adhesive strength between the surfaces of thefifth insulation layer 126 and the sixth insulation layer 228. Thethermal treatment may be performed at a temperature of about 300° C. toabout 700° C.

As illustrated in FIG. 15, the gates of the transfer transistors 214 mayprotrude downwardly (that is, toward the first substrate 100) from thefirst surface A of the second substrate 200. The fifth and the sixthwirings 224 and 220 being electrically connected to the transfertransistor 214 may be placed below the transfer transistor 214. Anywirings may be not placed above the photodiode 210.

The sixth insulation layer 228, the seventh insulation layer 222 and theeighth insulation layer 218 are sequentially disposed on the fifthinsulation layer 126. The fifth wiring 224 may be placed between thesixth insulation layer 228 and the seventh insulation layer 222, and thesixth wiring 220 may be placed between the seventh insulation layer 222and the eighth insulation layer 218.

In conventional techniques, a metal layer or a metal pattern is exposedon at least one of adhesion surfaces of a first substrate and a secondsubstrate. In this case, dishing easily occurs on a surface of the metallayer during a planarization process performed on the adhesion surfacesof the first substrate and the second substrate before adhering thefirst substrate to the second substrate. That is, the metal layer maynot have level surface. The metal layer may have a sink around a centerof the metal layer. It is hard to adhere the first substrate to thesecond substrate around where dishing occurred. Additionally, the metallayer is easily oxidized during the thermal treatment process. When themetal layer is oxidized, a resistance of the metal layer increases at anoxidized region and the adhering process is not performed well.

In contrast, according to some embodiments, metal material is notexposed on the fifth insulation layer 126 and the sixth insulation layer228. Only oxide such as silicon oxide is exposed on the fifth insulationlayer 126 and the sixth insulation layer 228. Therefore, the problemsdescribed above may not occur.

Referring to FIG. 16, a second surface B of the second substrate 200 isremoved by a polishing process, such that only the single crystallinesilicon layer 200 a is remained, in which the second surface Bcorresponds to the first surface A. The second substrate 200 a remainedafter the polishing process may have a thickness less than about 7,000Å.

Referring to FIG. 17, a photo resist pattern 231 is formed on the secondsurface B of the second substrate 200 a. The photo resist pattern 231may partially expose the second surface B. Portions of the secondsurface B being exposed by the photo resist pattern 231 may correspondto the sacrificial plugs 230. A protective layer (not illustrated) maybe further formed on the second surface B to protect the secondsubstrate 200 a.

Second contact holes 232 are formed by etching portions of the secondsubstrate 200 a exposed by the photo resist pattern 231. The secondcontact holes 232 may expose upper surfaces of the sacrificial plugs230.

Referring to FIG. 18, the photo resist pattern 231 and the sacrificialplugs 230 are removed simultaneously by an ashing process. A thirdcontact holes 234 being deeper than the second contact holes 232 may beformed when the sacrificial plugs 230 are removed.

As described above, the sacrificial plugs 230 may be removed without anadditional etching process.

Referring to FIG. 19, fourth contact holes 235 are formed by etchingportions of the sixth insulation layer 228 and the fifth insulationlayer 126 exposed by the third contact holes 234. The fourth contactholes 235 may expose upper surfaces of the fourth wiring 124. The fourthcontact holes 235 may penetrate the second substrate 200 a, the eighthinsulation layer 218, the seventh insulation layer 222, the sixthinsulation layer 228 and the fifth insulation layer 126 from the secondsurface B of the second substrate 200 a. At least one of the fifthwiring 224 and the sixth wiring 220 may be exposed on a sidewall of thefourth contact holes 235.

The fourth contact holes 235 may have a depth of about 10,000 Å to about25,000 Å. As described above, the fourth contact holes 235 may be formedby two etching processes and one ashing process. An etched depth by oneetching process may be only in a range of about 2,000 Å to about 6,000Å. Therefore, the fourth contact holes 235 may be easily formed by theprocesses described above.

Referring to FIG. 20, an additional insulation layer 237 (FIG. 33) isformed on a sidewall of upper portions of the fourth contact holes 235.A conductive material may be deposited to fill up the fourth contactholes 235. The conductive material may be planarized to form the contactplugs 236. The conductive material may include metal and/or metalcompound. Since the second substrate 200 a is exposed on the sidewall ofupper portions of the fourth contact holes 235, the additionalinsulation layer 237 may insulate the contact plugs 236 from the secondsubstrate 200 a.

The contact plugs 236 may penetrate the eighth insulation layer 218, thesixth wiring 220, the seventh insulation layer 222, the fifth wiring 224and the sixth insulation layer 228 on the second substrate 200 a, andpenetrate the fifth insulation layer 126 on the first substrate 100. Thecontact plugs 236 may be electrically connected to the fourth wiring124. Therefore, signals applied to the sixth wiring 220 and the fifthwiring 224 may be transferred to the fourth wiring 124 through thecontact plugs 236.

FIG. 21 is a cross-sectional view of an image sensor in accordance withsome embodiments.

The image sensor of FIG. 21 is similar to the image sensor of FIG. 3,except that etching stop layers are provided on upper surfaces and lowerlateral surfaces of the wirings.

Referring to FIG. 21, a first substrate 100 may include a singlecrystalline material. For example, the first substrate 100 may includesingle crystalline silicon, single crystalline germanium, etc. A resettransistor 102, a driving transistor 104, a selection transistor 106 anda logic transistor 108 are provided on the first substrate 100. Thetransistors 102, 104, 106 and 108 may include a gate insulation layer, agate electrode and impurity regions. A spacer may be provided on asidewall of each gate electrode.

A first insulation layer 110, a second insulation layer 114, a thirdinsulation layer 118, a fourth insulation layer 122 and a fifthinsulation layer 126 covering the transistors 102, 103, 106 and 108 aresequentially disposed on the first substrate 100. A first wiring 112, asecond wiring 116, a third wiring 120 and a fourth wiring 124 are formedthrough the first to the fifth insulation layers 110, 114, 118, 122 and126, respectively. The first to the fourth wirings 112, 116, 120 and 124may be electrically connected to the transistors 102, 104, 106 and 108on the first substrate 100. Each of the first to the fourth wirings 112,116, 120 and 124 includes a contact plug and a conductive pattern.

A photodiode 210, a transfer transistor 214 and a floating diffusionlayer 212 are provided on a second substrate 200 a. An eighth insulationlayer 218, a seventh insulation layer 222 and a sixth insulation layer228, which cover the photodiode 210, the transfer transistor 214 and thefloating diffusion layer 212, are successively disposed under a firstsurface of the second substrate 200 a. A sixth wiring 220 and a fifthwiring 224 are disposed through the eighth to the sixth insulationlayers 218, 222 and 228 to be electrically connected to the transfertransistor 214 and the floating diffusion region 212. Each of the sixthand the fifth wirings 220 and 224 includes a contact plug and aconductive pattern.

The contact plugs and the conductive patterns included in the first tothe sixth wirings 112, 116, 120, 124, 224 and 220 may include copperhaving a low resistance. When the first to the sixth wirings 112, 116,120, 124, 224 and 220 are formed using copper having a low resistance,the first to the sixth wirings 112, 116, 120, 124, 224 and 220 may haverelatively small widths and heights. Therefore, thicknesses of the firstto the eighth insulation layers 110, 114, 118, 122, 126, 228, 222 and218 may be reduced and a total height of the image sensor may also bereduced.

Etching stop layers 140 are provided on upper surfaces and lower lateralsurfaces of the conductive patterns included in the first to the fourthwirings 112, 116, 120 and 124. Etching stop layers 260 are provided onupper surfaces and lower lateral surfaces of the conductive patternsincluded in the sixth and the fifth wirings 220 and 224. The etchingstop layers 140 and the etching stop layers 260 formed on the uppersurfaces of the conductive patterns may serve as diffusion barrierlayers for preventing metal included in the conductive patterns fromdiffusing. As illustrated in FIG. 21, the etching stop layers 140 may beprovided on each boundary surfaces between the first to the fifthinsulation layers 110, 114, 118, 122 and 126, and the etching stoplayers 260 may be provided on each boundary surfaces between the eighthto the sixth insulation layers 218, 222 and 228. The etching stop layers140 and the etching stop layers 260 may include silicon nitride.

Similar to the image sensor of FIG. 3, the fifth insulation layer 126 onthe first substrate 100 and the sixth insulation layer 228 on the secondsubstrate 200 a are adhered to each other. The fifth insulation layer126 and the sixth insulation layer 228 may include silicon oxide. Acontact plugs 236 may penetrate the eighth insulation layer 218, thesixth wiring 220, the seventh insulation layer 222, the fifth wiring 224and the sixth insulation layer 228 on the second substrate 200 a, andpenetrate the fifth insulation layer 126 on the first substrate 100 tobe electrically connected to the fourth wiring 124. An anti-reflectivelayer 238, a color filter 240 and a micro lens 242 are provided on asecond surface of the second substrate 200 a in which the second surfacecorresponds to the first surface.

In some embodiments, the image sensor may have a low height and a highperformance since the first to the sixth wirings 112, 116, 120, 124, 224and 220 are formed using copper having a low resistance. Additionally,since the first to the sixth wirings 112, 116, 120, 124, 224 and 220 aredisposed below the photodiode 210, a light incident on the photodiode210 may be not reduced although the etching stop layers 140 and 260,which are formed using silicon nitride having a lower lighttransmittance than silicon oxide, are formed on the first to the sixthwirings 112, 116, 120, 124, 224 and 220.

FIGS. 22 to 27 are cross-sectional views illustrating methods ofmanufacturing an image sensor in accordance with some embodiments.

The methods of manufacturing the image sensor of FIGS. 22 to 27 aresimilar to the methods of manufacturing the image sensor of FIGS. 5 to20, except that wirings are formed by a damascene method.

Referring to FIG. 22, the photodiode 210, the transfer transistor 214and the floating diffusion region 212 are formed on the second substrate200 by the same processes as described with reference to FIG. 5.

A first lower insulation layer 218 a covering the photodiode 210, thetransfer transistor 214 and the floating diffusion region 212 is formed.An etching stop layer 260 a is formed on the first lower insulationlayer 218 a. The etching stop layer 260 a may include silicon nitride. Afirst upper insulation layer 218 b is formed on the etching stop layer260 a.

First trenches 252 a may be formed around a region where the firstconductive pattern will be formed. The first trenches 252 a may beformed by etching the first upper insulation layer 218 b and the etchingstop layer 260 a. Regions of the first upper insulation layer 218 b andthe etching stop layer 260 a where the contact plug 236 that penetratesthe first conductive pattern will be formed are not removed during theprocess of forming the first trenches 252 a. Fifth contact holes 252 bmay be formed by etching portions of the first lower insulation layer218 a under the first tranches 252 a.

Referring to FIG. 23, a barrier metal layer (not illustrated) is formedon the first trenches 252 a, the fifth contact holes 252 b and the firstupper insulation layer 218 b. The barrier metal layer may include one oftitanium, titanium nitride, tantalum, tantalum nitride, etc., or may beformed by accumulating more than two of titanium, titanium nitride,tantalum, tantalum nitride, etc. Metal may be deposited on the barriermetal layer to fill up the fifth contact holes 252 b and the firsttrenches 252 a. It is hard to pattern the metal by a photolithographyprocess. For example, the metal may be copper.

After that, the barrier metal layer may be polished by a chemicalmechanical polishing (CMP) process to expose the first upper insulationlayer 218 b for forming the sixth wiring 220.

An etching stop layer 260 b is formed on the sixth wiring 220 and thefirst upper insulation layer 218 b. The etching stop layer 260 b mayserve as a diffusion barrier layer for preventing metal included in thesixth wiring 220 from diffusing.

Referring to FIG. 24, a second lower insulation layer 222 a, an etchingstop layer 260 c, a second upper insulation layer 222 b and an etchingstop layer 260 d are sequentially formed by the same processes asdescribed with reference to FIGS. 22 and 23. The fifth wiring 224electrically connected to some of the sixth wiring 220 may be formed.Regions of the second upper insulation layer 222 b and the etching stoplayer 260 c where the contact plug 236 will be formed are not removedduring the process of forming the fifth wiring 224.

Referring to FIG. 25, contact holes are formed to expose the firstsurface of the second substrate 200 by etching the regions of theinsulation layers and the etching stop layers where the contact plug 236will be formed. After that, the sacrificial plugs 230 may be formed bydepositing a sacrificial layer in the contact holes. The sixthinsulation layer 228 may be formed on the sacrificial layer 230 and theetching stop layer 260 d. The contact holes, the sacrificial plug 230and the sixth insulation layer 228 may be formed by the same processesas described with reference to FIGS. 8, 9 and 10.

Referring to FIG. 26, the reset transistor 102, the driving transistor104 and the selection transistor 106 are formed in the active pixelregion of the first substrate 100 and the transistor 108 included in thelogic circuits is formed in the logic region of the first substrate 100by the same processes as described with reference to FIG. 11.

The third lower insulation layer 110 a covering the transistors 102,104, 106 and 108 on the first substrate 100 is formed. The etching stoplayer 140 a and the third upper insulation layer 110 b are formed on thethird lower insulation layer 110 a.

Second trenches are formed at a region where the conductive pattern willbe formed. The second trenches are formed by etching the third upperinsulation layer 110 b and the etching stop layer 140 a. Sixth contactholes may be formed by etching portions of the third lower insulationlayer 110 a under the second tranches.

A barrier metal layer (not illustrated) is formed on the secondtrenches, the sixth contact holes and the third upper insulation layer110 b. Metal may be deposited on the barrier metal layer to fill up thesixth contact holes and the second trenches. It is hard to pattern themetal by a photolithography process. For example, the metal may becopper.

After that, the barrier metal layer may be polished by a chemicalmechanical polishing (CMP) process to expose the third upper insulationlayer 110 b for forming the first wiring 112. An etching stop layer 140b is formed on the first wiring 112 and the third upper insulation layer110 b.

The insulation layers and the wirings are formed by repeatedlyperforming the same processes described above.

Referring to FIG. 27, the fifth insulation layer 126 on the firstsubstrate 100 and the sixth insulation layer 228 on the second substrate200 are adhered to each other by aligning, contacting and compressingthe fifth insulation layer 126 and the sixth insulation layer 228, andperforming a thermal treatment on two compressed insulation layers. Atleast a portion of the fourth wiring 124 on the first substrate 100 maycorrespond to the sacrificial plug 230 on the second substrate 200. Theprocesses for adhering the first substrate 100 and the second substrate200 to each other may be the same as the processes described withreference to FIG. 15.

After that, the second surface of the second substrate 200 a may bepolished, and the contact plugs 236 connected to the fourth wiring 124may be formed. The processes described above may be the same as theprocesses described with reference to FIGS. 16 to 20.

As described above, highly integrated image sensor may be provided byadhering two substrates to each other. Any conductive materials are notexposed on the surfaces of the fifth insulation layer 126 and the sixthinsulation layer 228. Only oxide such as silicon oxide is exposed on thesurfaces of the fifth insulation layer 126 and the sixth insulationlayer 228. Therefore, the first and the second substrates 100 and 200 amay be adhered to each other firmly.

The present inventive concept may be applied to various circuits havingtwo substrates adhered to each other. Hereinafter, a metal-oxidesemiconductor (CMOS) transistor having two substrates adhered to eachother will be described.

FIG. 28 is a circuit diagram illustrating an inverter including a CMOStransistor. FIG. 29 is a cross-sectional view of an inverter including aCMOS transistor in accordance with some embodiments.

In FIG. 29, a reference numeral 350 represents elements formed on afirst substrate 300 and a reference numeral 450 represents elementsformed on a second substrate 400.

Referring to FIG. 29, the first substrate 300 includes an active regionand an isolation region separated by an isolation layer 302. An N-typemetal-oxide semiconductor (NMOS) transistor 304 is formed in the activeregion of the first substrate 300. The NMOS transistor 304 may include afirst gate 304 a and N-type impurity regions 304 b disposed beneath asurface of the first substrate 300 around both sides of the first gate304 a. A channel region of the NMOS transistor 304 may be doped withP-type impurities. That is, a region of the first substrate 300 underthe first gate 304 a may be doped with P-type impurities.

A first insulation layer 306 covering the NMOS transistor 304 isprovided on the first substrate 300. First wirings 308 which penetratethe first insulation layer 306 and are electrically connected toelectrodes of the NMOS transistor 304 are provided.

A second insulation layer 310 covering the first wirings 308 is providedon the first insulation layer 306. Second wirings 312 which penetratethe second insulation layer 310 and are electrically connected to thefirst wirings 308 are provided. The second wirings 312 will be directlyconnected to wirings formed on the second substrate 400. Therefore, thesecond wirings 312 may have a shape extending in a directionsubstantially parallel to the first substrate 300 to increase an alignmargin.

A third insulation layer 314 covering the second wirings 312 is providedon the second insulation layer 310. The third insulation layer 314 maybe formed using a silicon oxide and have a level upper surface.

An isolation layer 402 is formed in the second substrate 400 from afirst surface of the second substrate 400. A P-type metal-oxidesemiconductor (PMOS) transistor 404 is formed on the first surface ofthe second substrate 400. The second substrate 400 may be formed usingsingle crystal silicon. A thickness of the second substrate 400 may bein a range of about 2,000 Å to about 5,000 Å. The PMOS transistor 404may include a second gate 404 a and P-type impurity regions 404 bdisposed beneath the first surface of the second substrate 400 aroundboth sides of the second gate 404 a. The second gate 404 a of the PMOStransistor 404 may protrudes downwardly (that is, toward the firstsubstrate 300) from the first surface of the second substrate 400.

A fifth insulation layer 406 covering the PMOS transistor 404 isprovided on the first surface of the second substrate 400. Third wirings408 which penetrate the fifth insulation layer 406 and are electricallyconnected to electrodes of the PMOS transistor 404 are provided.

A fourth insulation layer 410 covering the third wirings 408 is providedon a lower surface of the fifth insulation layer 406. The fourthinsulation layer 410 may have a level lower surface. The lower surfaceof the fourth insulation layer 410 may be adhered to the thirdinsulation layer 314 on the first substrate 300.

First contact plugs 412 that penetrate the second substrate 400, thefifth insulation layer 406, the third wiring 408, the fourth insulationlayer 410 and the third insulation layer 314 from a second surface ofthe second substrate 400 and are electrically connected to the secondwirings 312 are provided in which the second surface corresponds to thefirst surface. An insulation material (not illustrated) is provided onboundary surfaces between sidewalls of upper portions of the firstcontact plugs 412 and the second substrate 400.

A second contact plug 414 that penetrates the second substrate 400 fromthe second surface of the second substrate 400 and is electricallyconnected to one of the impurity regions 404 b of the PMOS transistor404 may be provided. An insulation material (not illustrated) isprovided on a boundary surface between sidewalls of the second contactplug 414 and the second substrate 400.

FIGS. 30 and 31 are cross-sectional views for describing methods ofmanufacturing a CMOS transistor of FIG. 29.

Referring to FIG. 30, the first substrate 300 includes the active regionand the isolation region separated by an isolation process. The NMOStransistor 304 is formed on the first substrate 300.

The first insulation layer 306 covering the NMOS transistor 304 and thefirst substrate 300 is formed. The first wirings 308 which penetrate thefirst insulation layer 306 and are electrically connected to electrodesof the NMOS transistor 304 are formed.

The second insulation layer 310 covering the first wirings 308 is formedon the first insulation layer 306. Second wirings 312 which penetratethe second insulation layer 310 and are electrically connected to thefirst wirings 308 are formed. The second wirings 312 will be directlyconnected to wirings formed on the second substrate 400. Therefore, thesecond wirings 312 may have a shape extended in a horizontal plane toincrease an align margin.

An insulation material may be deposited on the second insulation layer310 to cover the second wirings 312. The insulation material may beplanarized to expose an upper surface of the second wirings 312. Thethird insulation layer 314 having a level upper surface may be formed bydepositing an insulation material again to cover the second wirings 312.

Referring to FIG. 31, the PMOS transistor 404 is formed on the firstsurface of the second substrate 400. The PMOS transistor 404 may includethe second gate 404 a and the P-type impurity regions 404 b disposedbeneath the first surface of the second substrate 400 around both sidesof the second gate 404 a.

The fifth insulation layer 406 covering the PMOS transistor 404 isprovided on the first surface of the second substrate 400. The thirdwirings 408 which penetrate the fifth insulation layer 406 and areelectrically connected to electrodes of the PMOS transistor 404 areformed.

First contact holes that penetrate conductive patterns included in thethird wirings 408 and expose the first surface of the second substrate400 may be formed by a photolithography process. Sacrificial plugs 418may be formed in the first contact holes by depositing a sacrificiallayer in the first contact holes and planarizing the sacrificial layer.

The fourth insulation layer 410 having a level upper surface is formedon the fifth insulation layer 406.

Referring again to FIG. 29, the third insulation layer 314 on the firstsubstrate 300 and the fourth insulation layer 410 on the secondsubstrate 400 may be adhered to each other. At least a portion of thesecond wiring 312 on the first substrate 300 may correspond to thesacrificial plug 418 on the second substrate 400. The third insulationlayer 314 and the fourth insulation layer 410 may be adhered to eachother by the processes described with reference to FIG. 15.

The second surface of the second substrate 400 may be removed by apolishing process. Second contact holes that expose the sacrificialplugs 418 may be formed by etching the second surface of the secondsubstrate 400. Third contact holes may be formed by removing thesacrificial plugs 418 and then removing the fourth insulation layer 410and the third insulation layer 314 disposed under the sacrificial plugs418. Upper surfaces of the second wirings 312 on the first substrate 300may be exposed by the third contact holes. An insulation layer (notillustrated) is formed on a sidewall of upper portions of the thirdcontact hole. The first contact plugs 412 may be formed by depositing aconductive material in the third contact holes and polishing theconductive material.

A fourth contact hole may be formed in the second substrate 400 from thesecond surface of the second substrate 400. The second contact plug 414that is electrically connected to one of the impurity regions 404 b ofthe PMOS transistor 404 may be formed by depositing a conductivematerial in the fourth contact hole and polishing the conductivematerial.

As described above, a semiconductor device may be formed by adhering twosubstrates each of which has an insulation layer including silicon oxideas an adhered surface. The two substrates may be electrically connectedby a contact plug.

Since the sacrificial plug, which is easily removed by an ashingprocess, may be formed in the second substrate, a deep contact plughaving a depth more than about 5,000 Å may be easily formed. Since metalmaterial may be not exposed on the adhered surface, the two substratesmay be adhered to each other firmly.

FIG. 32 is a block diagram illustrating a system including an imagesensor in accordance with some embodiments.

Referring to FIG. 32, a system 700 processes an output image generatedfrom a CMOS image sensor 710.

The system 700 may be a computer system, a camera system, a scanner, amechanized clock system, a navigation system, a video phone, amonitoring system, an auto focusing system, a chase system, a motiondetection system, an image stabilization system, etc.

The system 700 includes a central process unit (CPU) 720, such as amicroprocessor, that communicates with an I/O device 730 through a bus705. The CMOS image sensor 710 may communicate with the CPU 720 througha bus 705. The system 700 may further include a memory RAM 740, a floppydisk drive 750, a CD ROM drive 755 and/or a port 760. The port 760 maycouple the system with a video card, a sound card, a memory card, auniversal serial bus (USB) device, etc. The port 760 may be acommunication port with which the system 700 communicates with anothersystem. The CMOS image sensor 710 may be integrated together with a CPU,a digital signal processor (DSP), a microprocessor, etc. A memory may befurther integrated with the CMOS image sensor. The CMOS image sensor maybe integrated in a chip that is different from a chip in which aprocessor is integrated.

As mentioned above, according to some embodiments, a highly integratedCMOS image sensor having a high performance may be provided. The CMOSimage sensor may be used in a digital camera, a camcorder, a personalcommunication system (PCS), a medical micro camera, a robot, etc.

The foregoing is illustrative of some embodiments and is not to beconstrued as limiting thereof. Although a few some embodiments have beendescribed, those skilled in the art will readily appreciate that manymodifications are possible in the some embodiments without materiallydeparting from the novel teachings and advantages of the presentinventive concept. Accordingly, all such modifications are intended tobe included within the scope of the present inventive concept as definedin the claims. Therefore, it is to be understood that the foregoing isillustrative of various some embodiments and is not to be construed aslimited to the specific some embodiments disclosed, and thatmodifications to the disclosed some embodiments, as well as other someembodiments, are intended to be included within the scope of theappended claims.

1. An image sensor comprising: a first substrate including a drivingelement; a first insulation layer on the first substrate and on thedriving element; a second substrate including a photoelectric conversionelement; a second insulation layer on the second substrate and on thephotoelectric conversion element, wherein a surface of the secondinsulation layer is on an upper surface of the first insulation layer;and a conductive connector penetrating the second insulation layer and aportion of the first insulation layer.
 2. The image sensor of claim 1,further comprising a first wiring pattern between the first substrateand the first insulation layer, a second wiring pattern between thesecond substrate and the second insulation layer, and a floatingdiffusion region in the second substrate, wherein the second wiringpattern is conductively connected to the floating diffusion region, andwherein the first wiring pattern is conductively connected to the secondwiring pattern by the conductive connector.
 3. The image sensor of claim1, wherein the driving element comprises a reset transistor, a drivingtransistor and a selection transistor, and wherein the photoelectricconversion element comprises a photodiode, a transfer transistor and afloating diffusion region, wherein the floating diffusion region isconductively connected to a gate of the driving transistor by theconductive connector.
 4. The image sensor of claim 3, wherein thefloating diffusion region is coupled to a source/drain region of thetransfer transistor.
 5. The image sensor of claim 3, wherein thefloating diffusion region provides a source/drain region of the transfertransistor.
 6. The image sensor of claim 3, wherein the floatingdiffusion region is conductively connected to a source/drain region ofthe reset transistor by the conductive connector.
 7. The image sensor ofclaim 3, further comprising a first wiring pattern between the firstsubstrate and the first insulation layer, and a second wiring patternbetween the second substrate and the second insulation layer, whereinthe second wiring pattern is conductively connected to the floatingdiffusion region, and wherein the first wiring pattern is conductivelyconnected to the second wiring pattern by the conductive connector. 8.The image sensor of claim 3, wherein the photodiode comprises a firstphotodiode and the transfer transistor comprises a first transfertransistor, the image sensor further comprising a second photodiode anda second transfer transistor in the second substrate, wherein thefloating diffusion region is coupled to source/drain regions of thefirst transfer transistor and the second transfer transistor.
 9. Theimage sensor of claim 8, wherein the floating diffusion region providessource/drain regions of the first transfer transistor and the secondtransfer transistor.
 10. The image sensor of claim 1, wherein theconductive connector is coupled to source/drain regions of four transfertransistors.
 11. A method of manufacturing an image sensor, comprising;forming a driving element on a first substrate; forming a firstinsulation layer on the first substrate and on the driving element;forming a photoelectric conversion element on a second substrate;forming a second insulation layer on the second substrate and on thephotoelectric conversion element; adhering the first substrate and thesecond substrate; and forming a conductive connector that penetrates thesecond insulation layer and a portion of the first insulation layer. 12.The method of claim 11, further comprising forming a first wiringpattern between the first substrate and the first insulation layer, asecond wiring pattern between the second substrate and the secondinsulation layer, and a floating diffusion region in the secondsubstrate, wherein the second wiring pattern is conductively connectedto the floating diffusion region, and wherein the first wiring patternis conductively connected to the second wiring pattern by the conductiveconnector.
 13. The method of claim 11, wherein the driving elementcomprises a reset transistor, a driving transistor and a selectiontransistor, and wherein the photoelectric conversion element comprises aphotodiode, a transfer transistor and a floating diffusion region,wherein the floating diffusion region is conductively connected to agate of the driving transistor by the conductive connector.
 14. Themethod of claim 13, wherein the floating diffusion region is coupled toa source/drain region of the transfer transistor.
 15. The method ofclaim 13, wherein the floating diffusion region is conductivelyconnected to a source/drain region of the reset transistor by theconductive connector.
 16. The method of claim 11, further comprising:forming at least two floating diffusion regions in the second substrate;and forming a wiring in the second insulation layer, the wiringelectrically connecting the at least two floating diffusion regions andthe conductive connector.
 17. The method of claim 11, furthercomprising: forming a wiring in the second insulation layer; forming avia hole that penetrates the wiring and a portion of the secondinsulation layer; forming a sacrificial connector in the via hole;etching a portion of the second substrate to expose the sacrificialconnector; removing the sacrificial connector; forming a contact hole byetching the second insulation layer and a portion of the firstinsulation layer disposed under the via hole; and depositing aconductive material in the contact hole.
 18. The method of claim 17,wherein the sacrificial connector comprises a polymer material includingcarbon.
 19. The method of claim 11, further comprising: polishing asurface of the second substrate opposite the first substrate afteradhering the first substrate and the second substrate, and forming acolor filter and a lens on the polished surface of the second substrate.20. The method of claim 13, wherein the photodiode comprises a firstphotodiode and the transfer transistor comprises a first transfertransistor, the method further comprising forming a second photodiodeand a second transfer transistor in the second substrate, wherein thefloating diffusion region is coupled to source/drain regions of thefirst transfer transistor and the second transfer transistor.